Question: When did Ibaraki Prefecture become head of government instead of Masaru Hashimoto?
Paraphrase: When did Ibaraki Prefecture replace Masaru Hashimoto as head of governement?
SPARQL (Wikidata): SELECT ?value WHERE { wd:Q83273 p:P6 ?s . ?s ps:P6 wd:Q982631 . ?s pq:P580 ?value}